1. Field of the Invention
The present invention relates to a microprocessor, and more specifically, to a debugging microprocessor used in a microprocessor development support system.
2. Description of Related Art
Heretofore, in order to debug a program under development, a target system to be debugged is coupled through a connector and cable to a microprocessor development support system which includes a debugging microprocessor and a controller so as to execute and debug a program under development instead of a microprocessor to be installed in the target system. In other words, the debugging microprocessor must execute a program stored in a memory of the target system to be debugged, and also a debugging program stored in another memory provided in the microprocessor development support system. In general, a microprocessor to be used in the target system to be debugged (called "target microprocessor" hereinafter) is used as a debugging microprocessor. In addition, in order to switch from the program to be debugged to the debugging program, a non-maskable interrupt (called "NMI" in some case hereinafter) for the target microprocessor is used.
Because of this non-maskable interrupt, the conventional microprocessor development support system using the target microprocessor as the debugging microprocessor could not have ensured a normal execution of the program to be debugged. Further, when the non-maskable interrupt from the target system to be debugged and the interrupt for break request concurrently occur, either one of these interrupts must be neglected. In addition, the save timing control for the non-maskable interrupt was very complicated.